// 练习1：使用fp.add(x, y)和fp.map(f, x)创建一个能让functor里的值增加的函数ex1
const fp = require('lodash/fp')
const { Maybe, Container } = require('./support')
let maybe = Maybe.of([5, 6, 1])

let ex1 = (maybe, number) => {
    return maybe.map(x => fp.map(fp.add(number), x))
}
console.log(ex1(maybe, 2));

// 练习2 实现一个函数ex2,能够使用fp.first获取列表的第一个元素
let xs = Container.of(['do', 'ray', 'me', 'fa', 'so', 'la', 'ti', 'do'])
let ex2 = (xs) => {
    let r = xs.map(x => x);
    return fp.first(r._value);
}
console.log(ex2(xs));


// 练习3：实现一个函数ex3,使用safeProp和fp.first找到user的名字的首字母
let safeProp = fp.curry(function(x, o) {
    return Maybe.of(o[x])
})
let user = { id: 2, name: 'Albert' }
let ex3 = (user) => {
    return fp.first(safeProp('name', user)._value);
}
// console.log('ex3', ex3(user));


//练习4：使用Maybe重写ex4，不要有if语句
let ex4 = function(n) {
    // if (n) {
    //     return parseInt(n);
    // }
    return Maybe.of(n).map(value => parseInt(value));
}
// console.log('ex4', ex4(null));